Interrupted time-series analysis for impacts of the vaccine immunization on the incidence of meningococcal meningitis in Hebei Province
Objective To evaluate the impact of meningococcal vaccine immunization on the incidence of meningococcal meningitis,aiming to refine the local immunization strategies and programs.Methods Data on the reported incidence of meningococcal meningitis in Hebei province for 1970-2023 were collected,and interrupted time-series(ITS)analysis was used to quantitatively analyze the levels and slope change of the incidence of meningococcal meningitis before and after vaccine immunization and before and after inclusion in the Expanded Program on Immunization(EPI).Results The annual average reported incidences of meningococcal meningitis in Hebei province before vaccination(1970-1979),before(1980-2007)and after(2008-2023)the inclusion of the vaccine in the EPI were respectively 20.79 per 100 000,1.66 per 100 000,and 0.018 per 100 000.The interrupted time-series analysis from 1970 to 2023 showed an initial meningitis incidence rate of 24.12 per 100 000(t=9.86,P<0.05),with an average annual decrease of 1.07 per 100 000(t=-2.42,P<0.05).After the introduction of the meningococcal vaccine in 1980,the incidence of meningococcal meningitis decreased quickly with an annual average decline of 18.39 per 100 000,showing a significant short-term intervention effect(t=-2.70,P<0.05);however,the rate of decrease slowed over the long term to 0.13 per 100 000,with the long-term intervention effect not being significant(P>0.05).And the incidence was significantly increased due to the outbreak(t=7.80,P<0.05).From 1980 to 2023,the initial level of incidence was 5.13 per 100 000(t=8.70,P<0.05),and decreased by 0.23/100 000 per year on average(t=-6.42,P<0.05).After the inclusion of the vaccine in the EPI in 2008,the rate of decrease further slowed down to an average of 0.008 per 100,000 per year,with the long-term intervention effect being significant(t=2.50,P<0.05);the impact of epidemic outbreaks on incidence during this period was not statistically significant(P>0.05).Conclusions Meningococcal meningitis vaccination has led to a general downward trend in the incidence of meningitis in Hebei Province,and has flattened the trend of increased incidence caused by outbreaks.Therefore,long-term maintenance in immunization programs on the meningococcal meningitis is necessary.In addition,it is important to strengthen the monitoring of the distribution of epidemic serogroups in patients and healthy carriers,and to adjust immunization strategies timely based on changes in bacterial populations,selecting and promoting vaccines accordingly for the prevalent strains.
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